A set of intruments of the aforementioned type is known. It has a straight catheter guide tube rounded off at its distal end. The interior of the reinforcing tube for the associated catheter is constructed so that it forms the inner surface of the straight catheter in the proximal area. Upon insertion into the uterus, this known, one-piece, flexible catheter guide tube, made from synthetic material, is stabilized by a metal mandrin. This mandrin shapes the uterus prior to inserting the catheter guide tube so that insertion is made easier. Of course, the catheter guide tube only maintains this shape as long as the mandrin is located inside the tube. The reinforcing tube prevents the catheter from bending through the effect of the weight of a syringe placed in the connection for the syringe on the catheter. It has been shown that a disadvantage of this known set of instruments is that upon introducing the catheter guide tube into the uterus, it is almost impossible to avoid injuring the endometrium. The distal end of the catheter guide tube cuts into the endometrium causing it to bleed. With actual embryo transfer it has been shown that there is a not insignificant danger of injury to the embryos from the surface of the reinforcing tube. This can be put down to the relatively rough surface of the drawn metal reinforcing tube. Further, as a successful embryo transfer cannot be performed with an injured endometrium the success rate when using this known set of instruments must be regarded as extremely low.
With a set of instruments for uterine embryo transfer which differs from the above-mentioned type in that the catheter does not have a metal reinforcing tube but, on the contrary, the proximal area of which is stabilized through the use of only two flexible tubes arranged in a coaxial fashion, a catheter guide tube is provided with an acorn-shaped tip. This catheter guide tube can be inserted in the uterus using a flexible mandrin even without the necessity of prior shaping.
This means that, upon insertion into the uterus, the catheter guide tube is also relatively flexible and the danger of injuring the endometrium is reduced. On the other hand, there is the not low probability that just the acorn-shaped distal end of the catheter guide tube could penetrate and thereby injure the endometrium. Here it is especially the sharp edge between the tapering surface of the"acorn" and the outlet of the catheter which is significant. Of course, the omission of an actual reinforcing tube for the catheter is a disadvantage. Despite the two coaxial flexible tubes the catheter can bend under the weight of an attached syringe and thus be pulled out of the catheter guide tube in an uncontrolled manner with the likelihood of being damaged. Naturally, both of these possibilities are extremely undesirable when performing a uterine embryo transfer or intra-uterine insemination.
With the known set of instruments the catheter guide tube is provided with a movable stop in its distal area for positioning in the portio.
A set of instruments for transvaginal gamete transfer and for catheterization of the fallopian tubes has a catheter guide tube with a bend in the distal area, the distal end of which finishes in a ball. The bend is provided in order to make the insertion of the catheter guide tube into the entrance to the fallopian tubes easier. The ball centres the outlet for the catheter in the tube.
Teflon is known as a material for embryo transfer catheters and the associated catheter guide tubes. Teflon can be employed for the formation of smooth surfaces which are advantageous.